Publications in Scientific Journals:
E. Wolfrum, M. Bernert, J. Boom, A. Burckhart, I. Classen, G. Conway, T. Eich, R. Fischer, A. Gude, A. Hermann, N. Luhmann Jr., M. Maraschek, R. McDermott, H. Park, T. Pütterich, J. Vicente, B. Wieland, M. Willensdorfer, . ASDEX Upgrade Team:
"Characterization of edge profiles and fluctuations in discharges with type-II and nitrogen-mitigated edge localized modes in ASDEX Upgrade";
Plasma Phys. Control. Fusion,
Edge localized modes (ELMs) with high frequency and low power loss (type-II
ELMs) occur in high triangularity, near double null configurations in ASDEX
Upgrade with full tungsten plasma facing components. The transition from
type-I to type-II ELMs is shown to occur above a collisionality threshold. For
the first time the characteristic MHD fluctuations around 40 kHz have been
localized. The fluctuations are observed in a wide region extending from the
pedestal inward to normalized poloidal radius ρpol = 0.7. Their amplitudes on
the low-field side of the plasma exhibit maxima above and belowthe mid-plane.
The fluctuations move in the electron drift direction and lead to a reduced edge
electron temperature gradient. The reduction in the edge pressure gradient is
connected with these MHD fluctuations, which affect the electron temperature
but not the electron density profiles. A comparison with nitrogen-mitigated
type-I ELMs in the same plasma shape shows that core profiles are also affected.
The electron temperature profile is self-similar for type-I and nitrogen-mitigated
type-I ELMs but is not self-similar in the case of type-II ELMs.
(Some figures in this article are in colour only in the electronic version)
Created from the Publication Database of the Vienna University of Technology.